1. Field of Invention
This invention relates to noise suppression devices and more particularly to noise suppression devices utilized in motor vehicles.
2. Description of the Prior Art
In recent years automobiles have been equipped with various kinds of electronic systems such as FM radios, radiotransmitters, electrically controlled fuel injection devices, etc. Since the systems operate with signals in the high frequency range, they are vulnerable to adverse effects caused by high frequency noise currents steming from the ignition system, voltage regulator, and various other kinds of manual and automatic switches (horn relays, turn signals, etc.). These harmful effects, are, for instance, noise in the radio signal, malfunction or loss of function of the system, etc. Accordingly, it has become frequently necessary to provide some remedy to eliminate these harmful effects.
In the prior art, it has become practice to suppress the noise by preventing noise generation itself by means of an anti-noise device such as a capacitor that bypasses high frequency noise currents at their sources or by avoiding any coupling of a wire that passes noise currents with another wire that is coupled to an electronic device which would be vulnerable to noise effects. The latter of noise prevention methods is effective when a high frequency noise current is being coupled from one wire to another. In this case the noise prevention is achieved by either increasing the distance between the two wires or by reducing this coupling, using, for example, a shielded wire. Previously used methods, however, have not proven fully effective and are also associated with drawbacks such as increased vehicle cost due to installation of additional special equipment and increased space requirements for the special equipment and redesign of the electrical wiring harness, etc..